Carboxyl group-modified cellulose or acryl fiber and process of producing same

Abstract: Cellulose or acrylonitrile fiber having methacrylic acid or hydroxyalkyl methacrylate graft-copolymerized in an amount of 3-60 % by weight is disclosed. The graft fiber is produced by reacting methacrylic acid or a hydroxyalkyl methacrylate with cellulose or acrylonitrile fiber in an aqueous medium containing hydrogen peroxide and a ferrous salt.

Description: This invention relates generally to a fiber modified with carboxyl groups and, more specifically, to an acrylonitrile fiber to which methacrylic acid or a hydroxyalkyl methacrylate is graft-copolymerized. The present invention is also directed to a process for producing such a modified fiber. An acrylonitrile fiber has properties similar to wool but has a defect that its moisture or damp absorbing power is poor. No effective method is however known to impart hydrophilicity to the acrylonitrile fiber. A method is known in which a vinyl monomer having an acidic group is graft-copolymerized to a polyester or polyamide fiber using an organic peroxide such as benzoyl peroxide. EP-A-0262405 discloses a process for preparing a water absorptive composite material in which an aqueous solution of a polymerizable monomer comprising acrylic acid (at least partly in the form of alkali metal or ammonium salts) is applied to a prefabricated fibrous substrate, polymerized in situ and then crosslinked by the addition of a crosslinking agent to the composite. The polymerizable monomer may also contain up to 20 mol % of optional comonomers and methacrylic acid, 2-hydroxyethyl methacrylate and 2-hydroxypropyl methacrylate are mentioned in that connection. The substrate material is preferably a cellulose or polyester fiber but may also be polyacrylonitrile. Textile Research Journal, 1989, (59), pages 525-529 reports a study of the graft copolymerization of methyl methacrylate onto chemically modified jute fibers using Fenton's reagent (Fe ++ /H 2 O 2 ). In accordance with the present invention there is provided a modified fiber comprising an acrylonitrile-series substrate fiber and a graft comonomer graft-copolymerized to said substrate fiber in an amount of 3-60% by weight based on the weight of said substrate fiber, said graft comonomer being at least one member selected from methacrylic acid and hydroxyalkyl methacrylate. In another aspect, the present invention provides a process for the production of a modified fiber, comprising graft-copolymerizing a graft comonomer to an acrylonitrile-series substrate fiber in an aqueous medium containing hydrogen peroxide and a source of ferrous ion, said graft comonomer being at least one member selected from methacrylic acid and hydroxyalkyl methacrylates. The present invention will now be described in detail below. The acrylonitrile fiber used in the present invention, may be in any desired form such as a yarn, a cotton, a woven or non-woven fabric, a filament or a tow. If desired, the substrate fiber may be used in combination with another fiber. The term "acrylonitrile-series fiber" used in the present specification and claims is intended to refer to a fiber formed of a homopolymer acrylonitrile or a copolymer of acrylonitrile with a vinyl comonomer. Examples of the vinyl comonomers include methyl acrylate, vinyl acetate, acrylic acid, methacrylic acid, vinyl chloride, vinylidene chloride, methylvinylpyridine, styrenesulfonic acid and mixtures thereof. The copolymer of acrylonitrile with the vinyl comonomer generally has a content of the acrylonitrile of at least 20% by weight, preferably 35-90% by weight. To the substrate fiber is graft-copolymerized and linked a graft comonomer in an amount of 3-60% by weight based on the weight of the substrate fiber. The graft comonomer is selected from acrylic acid and hydroxyalkyl methacrylate such as 2-hydroxyethyl methacrylate and 2-hydroxypropyl methacrylate. The graft comonomer is preferably copolymerized in an amount of 5-40% by weight. The modified fiber according to the present invention may be prepared by graft-copolymerizing the graft comonomer to the substrate fiber in an aqueous medium containing hydrogen peroxide and a source of ferrous ion. The ferrous ions source is preferably a ferrous salt such as ferrous sulfate, ferrous chloride, ammonium ferrous sulfate or ferrous nitrate. The ferrous in salt is preferably present in the aqueous medium in an amount providing a ferrous ion concentration of 0.5 to 5 mmol/liter, more preferably 0.7 to 1.6 mmol/liter. The concentration of the hydrogen peroxide in the aqueous medium is preferably 0.01 to 0.1 mol/liter, more preferably 0.01 to 0.06 mol/liter. The hydrogen peroxide and the ferrous ion source together serve to accelerate the graft copolymerization. The aqueous medium may contain an acid in an amount of 2 to 4 mmol/liter, preferably 2.5 to 3.5 mmol/liter, if desired. The acid serves to enhance the grafting rate of the graft comonomer. Examples of suitable acids include sulfuric acid, hydrochloric acid, phosphoric acid and formic acid. Further, the aqueous medium may further contain a sequestering agent such as EDTA, NTA or a phosphoric acid-type or sulfonic acid-type agent. The graft comonomer is generally used in an amount of 5-100 parts by weight, preferably 10-60 parts by weight, per 100 parts by weight of the substrate fiber and wherein the weight ratio of said aqueous medium to said substrate fiber is generally 5:1 to 50:1, preferably 5:1 to 15:1. The graft copolymerization is generally performed at a temperature and for a period of time so that the graft monomer is grafted to the substrate fiber in an amount of 3-60% by weight based on the weight of the substrate fiber. Preferably, the graft degree (weight percentage of the grafted comonomer based on the weight of the substrate fiber) is 5-40% by weight when a methacrylonitrile-series fiber is used as the substrate fiber. The graft copolymerization is generally performed at a temperature of 40°-110°C for 30-240 minutes, preferably at 70°-110°C for 30-180 minutes, more preferably 90°-100° for 60-90 minutes. If desired, the carboxy groups (-COOH) introduced into the substrate fiber by graft copolymerization of the graft comonomer may be converted into -COOM (M represents a cation) by reaction with a salt-forming cation. The cation may be, for example, sodium ion, calcium ion, ferrous ion, cupric ion, zinc ion, manganese ion, silver ion, quaternary ammonium ion or quaternary organic amine ion. The process according to the present invention uses a ferrous salt in a very small amount. Therefore, the modified fibers are not discolored and no specific step for the removal of the ferrous salt is required. Further, the reaction conditions for the modification treatment may be easily controlled so that the graft copolymerization can be homogeneously performed. The modified fibers of the present invention have improved hydrophilicity and serve to function as a good adsorbent not only for basic, bad odor substances such as ammonia and amines, but also for metal ions. The following examples will further illustrate the present invention. Percentages are by weight. Example 1 Into an aqueous solution (150 ml) containing 0.3 % of hydrogen peroxide, 0.02 % of ferrous sulfate, 1.5 % of methacrylic acid, 0.03 % a sequestering agent (Chelest NTB) and 0.06 % of sulfuric acid (50°Be), 10 g of acrylic fibers (Cashimiron 3Dx76V GK manufactured by Asahi Kasei Kogyo Co., Ltd.) were immersed. The mixture was gradually heated from room temperature to 100°C and maintained at that temperature for 1 hour. The treated fibers were washed well with water and dried to obtain modified acrylic fibers having a graft degree of 10.6 %. Example 2 Into an aqueous solution (100 ml) containing 0.5 % of hydrogen peroxide, 0.02 % of ferrous sulfate, 2.5 % of methacrylic acid, 0.05 % a sequestering agent (Chelest NTB) and 0.1 % of sulfuric acid (50°Be), 10 g of acrylic fibers (Kanebo Acryl WQ-1 1.8Dx76 mm, manufactured by Kanebo Co., Ltd.) were immersed. The mixture was gradually heated from room temperature to 100°C and maintained at that temperature for 1 hour. The treated fibers were washed well with water and dried to obtain modified acrylic fibers having a graft degree of 10.1 %. Example 3 Into an aqueous solution (150 ml) containing 0.5 % of hydrogen peroxide, 0.02 % of ferrous sulfate, 3 % of methacrylic acid, 0.05 % a sequestering agent (Chelest NTB) and 0.05 % of sulfuric acid (50°Be), 10 g of acrylic fibers (Toraylon 5x18 mm, manufactured by Toray Co., Ltd.) were immersed. The mixture was gradually heated from room temperature to 100°C and maintained at that temperature for 1 hour. The treated fibers were washed well with water and dried to obtain modified acrylic fibers having a graft degree of 9.6 %. Example 4 Example 3 was repeated in the same manner as described except that modacrylic fibers (Kanebo Acryl VE1 manufactured by Kanebo Co., Ltd.) was substituted for Toraylon. The modified acrylic fibers thus obtained had a graft degree of 8.1 %. Example 5 Example 1 was repeated in the same manner as described except that 2-hydroxyethyl methacrylate was substituted for methacrylic acid. The modified acrylic fibers thus obtained had a graft degree of 9.3 %. Example 6 Into an aqueous solution (100 ml) containing 0.5 % of hydrogen peroxide, 0.02 % of ferrous sulfate, 1.5 % of methacrylic acid, 1.5 % of 2-hydroxyethyl methacrylate, 0.05 % a sequestering agent (Chelest NTB) and 0.1 % of sulfuric acid (50°Be), 10 g of acrylic yarn (Silpalon 100d/-48f, manufactured by Mitsubishi Rayon Co., Ltd.) were immersed. The mixture was gradually heated from room temperature to 100°C and maintained at that temperature for 1 hour. The treated fibers were washed well with water and dried to obtain modified acrylic yarn weighing 114 % of the raw mterial yarn. The analysis of the carboxylic group revealed that the modified yarn had a grafted methacrylic acid monomber content of 6.4 %.

Claims: A modified fiber, comprising an acrylonitrile-series substrate fiber and a graft comonomer graft-copolymerized to said substrate fiber in an amount of 3-60% by weight based on the weight of said substrate fiber, said graft comonomer being at least one member selected from methacrylic acid and hydroxyalkyl methacrylate. A modified fiber as claimed in Claim 1, wherein said acrylonitrile-series fiber is a fiber formed of a homopolymer of acrylonitrile or a copolymer of acrylonitrile with a vinyl comonomer. A modified fiber as claimed in Claim 2, wherein said vinyl comonomer is selected from methyl acrylate, vinyl acetate, acrylic acid, methacrylic acid, vinyl chloride, vinylidene chloride, methylvinylpyridine and styrenesulfonic acid. A modified fiber as claimed in Claim 2 or Claim 3, wherein said copolymer has an acrylonitrile content of at least 20% by weight. A modified fiber as claimed in any preceding claim, wherein said hydroxyalkyl methacrylate is 2-hydroxyethyl methacrylate or 2-hydroxypropyl methacrylate. A process for the production of a modified fiber as defined in Claim 1, comprising graft-copolymerizing a graft comonomer to an acrylonitrile-series substrate fiber in an aqueous medium containing hydrogen peroxide and a source of ferrous ion, said graft comonomer being at least one member selected from methacrylic acid and hydroxyalkyl methacrylates. A process as claimed in Claim 6, wherein said source of ferrous ion is a ferrous salt. A process as claimed in Claim 7, wherein said ferrous salt is selected from ferrous sulfate, ferrous chloride, ammonium ferrous sulfate and ferrous nitrate. A process as claimed in Claim 7 or Claim 8, wherein said ferrous salt and said hydrogen peroxide are present in said aqueous medium in amounts of 0.5 to 5 mmol/liter and 0.01 to 0.1 mol/liter, respectively. A process as claimed in any one of Claims 6-9, wherein said graft comonomer is used in an amount of 5-100 parts by weight per 100 parts by weight of said substrate fiber, and wherein the weight ratio of said aqueous medium to said substrate fiber is from 5:1 to 50:1. A process as claimed in any one of Claims 6-10, wherein said graft copolymerization is performed at a temperature of 40°-110°C for a period of time so that said graft monomer is grafted to said substrate fiber in an amount of 3-60% by weight based on the weight of said substrate fiber.

Inventors: GOMIBUCHI REIZO, GOMIBUCHI, REIZO
Applicants: NIPPON SANMO SENSYOKU CO LTD, NIPPON SANMO SENSYOKU CO.,LTD.
Application year: 1994
Main classification: D06M14
IPC codes: D06M14